Acute stroke thrombolysis: time to dispense with the clock and move to tissue-based decision making?

Frequency, Characteristics, and Outcomes of Endovascular Thrombectomy in Patients With Stroke Beyond 6 Hours of Onset in US Clinical Practice

BACKGROUND AND PURPOSE

In 2018, 2 randomized controlled trials showed the benefit of endovascular thrombectomy (EVT) in acute ischemic stroke patients treated 6 to 24 hours from last known well using imaging-guided selection. However, little is known about outcomes in contemporary nontrial settings. We assessed the frequency of EVT and outcomes beyond 6 hours in the US Get With The Guidelines-Stroke clinical registry.

METHODS

We analyzed all acute ischemic stroke patients treated with EVT between January 1, 2009 and October, 1, 2018, at Get With The Guidelines-Stroke hospitals in the United States. We assessed trends over time in frequency of EVT beyond 6 hours, compared patient characteristics and outcomes between those treated within versus beyond 6 hours, and evaluated the associations between EVT time and outcomes.

RESULTS

We identified 53 702 patients at 697 sites treated with EVT during the study period. Treatment after 6 hours from last known well occurred in 17 720 (33%) of all 53 702 EVT cases (median 4.7 hours, interquartile range, 3.3-7 hours). The proportion of EVT cases treated after 6 hours from last known well varied widely across sites (median 30%, interquartile range, 24%-38%). Compared with patients treated within 6 hours, those treated beyond six hours were younger, less likely to have atrial fibrillation, less likely to arrive by ambulance, had lower stroke severity, were less likely to be anticoagulated, and more likely to be treated at centers with higher EVT volumes. After adjusting for patient and hospital characteristics, patients receiving EVT beyond 6 hours had less favorable in-hospital mortality, ambulation at discharge, and discharge disposition compared to those treated within 6 hours.

CONCLUSIONS

EVT is frequently performed for patients with ischemic stroke after 6 hours from last known well, accounting for one-third of cases nationally, and adjusted functional outcomes at discharge are worse in these patients compared to those treated with EVT within 6 hours. Further efforts are needed for optimal EVT outcomes in clinical practice settings.

Discrepancy between perfusion- and diffusion-weighted images in ischemic stroke: A case report

RATIONALE

With the development of multi-slice computed tomography (CT) technology, perfusion CT angiography (p-CTA) is now widely used for the diagnosis of acute cerebral infarction. Although p-CTA has the advantage of distinguishing between an ischemic penumbra and an infarct core, more research is needed with respect to its clinical use.

PATIENT CONCERNS

A healthy 36-year-old man experienced sudden dizziness while swimming. His dizziness persisted irrespective of the change in position, and then improved during transport. He had no neurological abnormality when he arrived at the emergency room.

DIAGNOSES

CT perfusion findings suggested left cerebellar infarction. P-CTA revealed a markedly delayed mean transit time, delayed time to peak, and increased cerebral blood volume in the left posterior inferior cerebellar artery territory at admission. However, the diffusion-weighted image (DWI) taken a few hours later revealed a large right cerebellar infarction.

INTERVENTIONS

Because of the time window, thrombolysis could not be performed and anti-platelet therapy was started.

OUTCOMES

Dysarthria and right-sided limb ataxia were newly developed before DWI (after p-CTA). Persistent foramen ovale was detected through transesophageal echography and identified as the cause of the stroke.

LESSONS

This case report suggests that dynamic image changes can occur within a short period of time depending on the vascular status and hemodynamic changes of the patients.

Accuracy of advanced CT imaging in prediction of functional outcome after endovascular treatment in patients with large-vessel occlusion

BACKGROUND AND PURPOSE

Computed tomography perfusion (CTP) and multiphase CT angiography (mCTA) help selection for endovascular treatment (EVT) in anterior ischemic stroke (AIS). Our aim was to investigate the ability of perfusion maps and collateral score to predict functional outcome after EVT.

PATIENTS AND METHODS

Patients with M1-middle cerebral artery occlusion, evaluated by mCTA and CTP and treated with EVT within six hours of onset, were enrolled. Perfusion parametric maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and time to maximum of tissue residue function ( T_max) were generated; areas of altered perfusion were manually outlined to obtain volumes CBF_v, CBV_v, Tmax,v16-25s and Tmax,v9.5-25s . Diffusion-weighted imaging (DWI) at 24-36 hours was used to manually outline the ischemic core (volume: DWI_v). Collateral vessels were assessed on mCTA considering extent and delay of maximal enhancement (six-point scale). Functional outcome was evaluated by modified Rankin Scale score at three months. Volumes in good and poor outcome groups were compared by Wilcoxon rank-sum test t, and their discriminative ability for outcome was determined by receiver operating characteristic analysis. A logistic regression model, including T_max, CBF and collaterals, was used to differentiate good and poor outcome.

RESULTS

Seventy-one patients (mean age 75 ± 11 years, range 45-99 years) were included. Tmax,v16-25s , Tmax,v9.5-25s , CBV_v, CBF_v and DWI_v were statistically different between the two groups. CBF had the best discriminative value for good and poor outcome (area under the curve (AUC) 0.73; 64.5% sensitivity; 74.4% specificity); the logistic regression model might be promising (AUC 0.79, 64.5% sensitivity, 82.1% specificity).

CONCLUSIONS

In patients with AIS, the combined use of CTP and mCTA predicts functional outcome of EVT and might allow better selection.

Susceptibility-weighted Imaging in Thrombolytic Therapy of Acute Ischemic Stroke

Objective:

To provide a comprehensive and latest overview of susceptibility-weighted imaging (SWI) in the application of thrombolysis in acute ischemic stroke, and to update the decision-making effect and clinical value of SWI on identifying stroke patients suitable for thrombolytic therapy and possible benefits and risks followed.

Data Sources:

Literatures referred to this review were collected from PubMed, Medline, and EMBASE published till May 2017, using the search terms including susceptibility-weighted imaging, gradient-echo, T2*, thrombolysis, recombinant tissue plasminogen activator (rt-PA), thrombolytic therapy, and stroke.

Study Selection:

Papers in English or with available English abstracts were considered, with no limitation of study design. References were also identified from the bibliographies of identified articles and the authors’ files.

Results:

SWI is of guiding significance for thrombolytic therapy in stroke patients, it can predict the location and length of thrombus and ischemic penumbra. It is worthy of noting that susceptibility vessel sign (SVS) on SWI can be used to predict recanalization after thrombolytic therapy and whether it is better to implement endovascular thrombolectomy in combination or alone. SWI is sensitive in detecting cerebral microbleed (CMB), and CMB might not be a contraindication for thrombolytic therapy, yet CMBs in multiple foci could possibly be related to intracranial hemorrhage (ICH) after thrombolysis. SVS and CMB on SWI sequence are of instructive value in performing antiplatelet therapy after thrombolytic therapy. Cerebral venous change on SWI is related to lower recanalization rate and poor outcome after thrombolysis.

Conclusions:

It seems that SWI can be applied to guide individualized thrombolytic therapies and assist clinicians in making better decisions by weighing benefits and risks. However, there still exist controversies about the relationship between signs on SWI and thrombolytic therapy.

Tissue Is More Important than Time in Stroke Patients Being Assessed for Thrombolysis

Aim

The relative prognostic importance of modern imaging profiles compared with standard clinical characteristics is uncertain in acute stroke patients. In this study, we aimed to compare baseline multimodal CT imaging measures with known clinical predictors of patient outcome at 3 months [modified Rankin scale (mRS)].

Methods

We collected baseline, 24 h, and day 90 clinical and imaging data from acute ischemic stroke patients being assessed for thrombolytic therapy between 2010 and 2015 at a single center as part of a retrospective analysis.

Results

561 patients presenting within 4.5 h of ischemic stroke onset who were eligible for thrombolysis based on standard clinical criteria were assessed. Acute infarct core volume on CTP was the strongest univariate predictor of patient outcome (mRS 0–2, R² 0.497, p < 0.001), followed by collateral grade (mRS 0–2, R² 0.281, p < 0.001). The strongest baseline clinical predictor of outcome was National Institutes of Health Stroke Scale (NIHSS) (mRS 0–2, R² = 0.203, p < 0.001). Time to treatment (mRS 0–2, R² 0.096, p = 0.01) and age (mRS 0–2, R² 0.027, p = 0.013) were relatively weak univariate baseline clinical predictors of 3-month outcome. In multivariate analysis, acute infarct core volume and collateral grade were the only significant baseline predictors of 3-month disability (both p < 0.001).

Conclusion

In patients assessed for thrombolysis by combined clinical and multimodal CT criteria within 4.5 h of onset, the size of the CTP infarct core and collateral grade on multimodal CT were highly predictive of patient outcome. Standard clinical variables, including time to treatment and NIHSS, were not as strongly predictive as multimodal CT variables.

Visibility of CT Early Ischemic Change Is Significantly Associated with Time from Stroke Onset to Baseline Scan beyond the First 3 Hours of Stroke Onset

Background and Purpose

Non-contrast brain computed tomography (NCCT) remains the most common imaging modality employed to select patients for thrombolytic therapy in acute ischemic stroke. The current study used the Alberta Stroke Program Early CT Score (ASPECTS) to identify early ischemic changes on brain NCCT imaging with the aim to investigate whether a relationship exists between time from symptoms onset to NCCT with the presence of early ischaemic change quantified by ASPECTS.

Methods

We studied 1,329 ischemic stroke patients who had NCCT within 8 hours of stroke onset. Patients were assessed to see if they had any ASPECTS lesion and if the rate of patients with a lesion increased with time using logistic regression.

Results

30% patients had an ASPECTS <10 within the first 3 hours from symptom onset. Within the first 3 hours, the odds for a CT change (ASPECTS <10) per minute of time was 1.00 with 95% confidence interval (CI) (0.99 to 1.00) (P=0.266). After 3 hours, there was a significant increase in odds of ASPECTS <10 with increasing time. The odds of being ASPECTS positive increased 1% (odds ratio=1.01) per 1 minute of time with 95% CI (1.00 to 1.01) (P=0.002).

Conclusions

We have identified that prior to first 3 hours of stroke there was no effect of time on odds of CT ischemic change; after the first 3 hours of stroke the odds increased with increasing time to CT scan. The occurrence of early ischemic change may be a marker of time from stroke onset rather than severity.

Perfusion computed tomography in patients with stroke thrombolysis

See Saver (doi:10.1093/awx020) for a scientific commentary on this article.

Stroke shortens an individual’s disability-free life. We aimed to assess the relative prognostic influence of pre- and post-treatment perfusion computed tomography imaging variables (e.g. ischaemic core and penumbral volumes) compared to standard clinical predictors (such as onset-to-treatment time) on long-term stroke disability in patients undergoing thrombolysis. We used data from a prospectively collected international, multicentre, observational registry of acute ischaemic stroke patients who had perfusion computed tomography and computed tomography angiography before treatment with intravenous alteplase. Baseline perfusion computed tomography and follow-up magnetic resonance imaging were analysed to derive the baseline penumbra volume, baseline ischaemic core volume, and penumbra salvaged from infarction. The primary outcome measure was the effect of imaging and clinical variables on Disability-Adjusted Life Year. Clinical variables were age, sex, National Institutes of Health Stroke Scale score, and onset-to-treatment time. Age, sex, country, and 3-month modified Rankin Scale were extracted from the registry to calculate disability-adjusted life-year due to stroke, such that 1 year of disability-adjusted life-year equates to 1 year of healthy life lost due to stroke. There were 772 patients receiving alteplase therapy. The number of disability-adjusted life-year days lost per 1 ml of baseline ischaemic core volume was 17.5 (95% confidence interval, 13.2–21.9 days, P < 0.001). For every millilitre of penumbra salvaged, 7.2 days of disability-adjusted life-year days were saved (β = −7.2, 95% confidence interval, −10.4 to −4.1 days, P < 0.001). Each minute of earlier onset-to-treatment time resulted in a saving of 4.4 disability-free days after stroke (1.3–7.5 days, P = 0.006). However, after adjustment for imaging variables, onset-to-treatment time was not significantly associated with savings in disability-adjusted life-year days. Pretreatment perfusion computed tomography can (independently of clinical variables) predict significant gains, or loss, of disability-free life in patients undergoing reperfusion therapy for stroke. The effect of earlier treatment on disability-free life appears explained by salvage of penumbra, particularly when the ischaemic core is not too large.

Computed tomography perfusion-based thrombolysis in wake-up stroke

Wake-up stroke (WUS) patients are typically excluded from reperfusion treatment, as the time of symptoms onset is unknown. The purpose of this study is to evaluate the clinical outcome and safety of intravenous thrombolysis with rt-PA in patients with WUS eligible for therapy using computed tomography perfusion criteria (CTP), compared to patients treated with rt-PA within 4.5 h of symptoms onset (non-WUS). This is an experimental, open-label trial, controlled against the best therapy currently in use. Primary endpoints were functional independence after 3 months [modified Rankin scale (mRS) ≤ 1] for clinical outcome and symptomatic intracerebral hemorrhage (SICH) for safety. Secondary endpoints were no or only mild disability after 3 months (mRS ≤ 2) for clinical outcome, total intracerebral hemorrhage (TICH) and contrast-induced nephropathy (CIN) for safety. 170 patients were treated, 143 non-WUS patients and 27 patients with WUS. Strokes of cardioembolic origin were most common in WUS patients (p < 0.001). Primary endpoints: mRS ≤ 1 was found in 35.8 % (non-WUS: 36.4% vs. WUS 33.3%; p = 0.62) and SICH was observed in 3.4 % of non-WUS patients and in WUS patients (p = 0.32). Secondary endpoints: mRS ≤ 2 was observed in 66.4 % of patients (non-WUS: 67.1% vs. WUS 62.9%; p = 0.67), TICH in 13.5 % of patients (13.9 % non-WUS vs. 11.1 % WUS; p = 0.69). CIN was documented in 3.7 % of WUS patients. rt-PA treatment carried out in WUS patients selected on the basis of CTP data demonstrate comparable clinical outcome and safety with respect to non-WUS patients. The study supports the hypothesis that a selected group of WUS patients may be suitable for thrombolysis.

Perfusion computed tomography to assist decision making for stroke thrombolysis

The use of perfusion imaging to guide selection of patients for stroke thrombolysis remains controversial because of lack of supportive phase three clinical trial evidence. We aimed to measure the outcomes for patients treated with intravenous recombinant tissue plasminogen activator (rtPA) at a comprehensive stroke care facility where perfusion computed tomography was routinely used for thrombolysis eligibility decision assistance. Our overall hypothesis was that patients with 'target' mismatch on perfusion computed tomography would have improved outcomes with rtPA. This was a prospective cohort study of consecutive ischaemic stroke patients who fulfilled standard clinical/non-contrast computed tomography eligibility criteria for treatment with intravenous rtPA, but for whom perfusion computed tomography was used to guide the final treatment decision. The 'real-time' perfusion computed tomography assessments were qualitative; a large perfusion computed tomography ischaemic core, or lack of significant perfusion lesion-core mismatch were considered relative exclusion criteria for thrombolysis. Specific volumetric perfusion computed tomography criteria were not used for the treatment decision. The primary analysis compared 3-month modified Rankin Scale in treated versus untreated patients after 'off-line' (post-treatment) quantitative volumetric perfusion computed tomography eligibility assessment based on presence or absence of 'target' perfusion lesion-core mismatch (mismatch ratio >1.8 and volume >15 ml, core <70 ml). In a second analysis, we compared outcomes of the perfusion computed tomography-selected rtPA-treated patients to an Australian historical cohort of non-contrast computed tomography-selected rtPA-treated patients. Of 635 patients with acute ischaemic stroke eligible for rtPA by standard criteria, thrombolysis was given to 366 patients, with 269 excluded based on visual real-time perfusion computed tomography assessment. After off-line quantitative perfusion computed tomography classification: 253 treated patients and 83 untreated patients had 'target' mismatch, 56 treated and 31 untreated patients had a large ischaemic core, and 57 treated and 155 untreated patients had no target mismatch. In the primary analysis, only in the target mismatch subgroup did rtPA-treated patients have significantly better outcomes (odds ratio for 3-month, modified Rankin Scale 0-2 = 13.8, P < 0.001). With respect to the perfusion computed tomography selected rtPA-treated patients (n = 366) versus the clinical/non-contrast computed tomography selected rtPA-treated patients (n = 396), the perfusion computed tomography selected group had higher adjusted odds of excellent outcome (modified Rankin Scale 0-1 odds ratio 1.59, P = 0.009) and lower mortality (odds ratio 0.56, P = 0.021). Although based on observational data sets, our analyses provide support for the hypothesis that perfusion computed tomography improves the identification of patients likely to respond to thrombolysis, and also those in whom natural history may be difficult to modify with treatment.

Susceptibility-diffusion mismatch predicts thrombolytic outcomes: a retrospective cohort study

BACKGROUND AND PURPOSE

Asymmetric hypointensity of cerebral veins on susceptibility-weighted imaging has been shown to indirectly reflect tissue hypoxia after cerebral ischemia. We therefore investigated whether patients with prominent asymmetry of the cerebral veins on SWI and a relatively small diffusion-weighted imaging lesion (SWI-DWI mismatch), representing the presence of salvageable tissue, were more likely to benefit from thrombolytic therapy.

MATERIALS AND METHODS

We conducted a retrospective study of the anterior circulation of patients with ischemic stroke with SWI/DWI acquired before thrombolysis. The asymmetry index was defined as the ratio of cerebral vein voxel count between the ischemic and normal hemisphere on the SWI phase map. We defined SWI-DWI mismatch as an asymmetry index score of ≥1.75 with a DWI lesion volume of ≤25 mL. Favorable outcome was defined as modified Rankin Scale 0-2 at 3 months. Univariate and multivariate logistic regression analyses were used to examine the association between the mismatch profile and favorable outcome.

RESULTS

Fifty-four patients undergoing thrombolytic treatment were enrolled in this study. The rate of favorable outcome was significantly higher among patients with baseline SWI-DWI mismatch compared with those without (78% versus 44%; adjusted odds ratio, 6.317; 95% CI, 1.12-35.80; P = .037). Patients with SWI-DWI mismatch were also more likely to have a favorable outcome from reperfusion (91% versus 43%, P = .033) or recanalization (100% versus 40%, P = .013). The accuracy of SWI-DWI mismatch for predicting favorable outcome was higher than that of perfusion-diffusion mismatch (63% versus 48.1%).

CONCLUSIONS

The presence of SWI-DWI mismatch may identify patients with ischemia who would benefit from early reperfusion therapy.

Defining acute ischemic stroke tissue pathophysiology with whole brain CT perfusion

BACKGROUND

This study aimed to identify and validate whole brain perfusion computed tomography (CTP) thresholds for ischemic core and salvageable penumbra in acute stroke patients and develop a probability based model to increase the accuracy of tissue pathophysiology measurements.

METHODS

One hundred and eighty-three patients underwent multimodal stroke CT using a 320-slice scanner within 6hours of acute stroke onset, followed by 24hour MRI that included diffusion weighted imaging (DWI) and dynamic susceptibility weighted perfusion imaging (PWI). Coregistered acute CTP and 24hour DWI was used to identify the optimum single perfusion parameter thresholds to define penumbra (in patients without reperfusion), and ischemic core (in patients with reperfusion), using a pixel based receiver operator curve analysis. Then, these results were used to develop a sigma curve fitted probability based model incorporating multiple perfusion parameter thresholds.

RESULTS

For single perfusion thresholds, a time to peak (TTP) of +5seconds best defined the penumbra (area under the curve, AUC 0.79 CI 0.74-0.83) while a cerebral blood flow (CBF) of < 50% best defined the acute ischemic core (AUC 0.73, CI 0.69-0.77). The probability model was more accurate at detecting the ischemic core (AUC 0.80 SD 0.75-0.83) and penumbra (0.85 SD 0.83-0.87) and was significantly closer in volume to the corresponding reference DWI (P=0.031).

CONCLUSIONS

Whole brain CTP can accurately identify penumbra and ischemic core using similar thresholds to previously validated 16 or 64 slice CTP. Additionally, a novel probability based model was closer to defining the ischemic core and penumbra than single thresholds.

Whole brain CT perfusion deficits using 320-detector-row CT scanner in TIA patients are associated with ABCD2 score

BACKGROUND

Transient ischemic attacks (TIA) are cerebral ischemic events without infarction. The uses of CT perfusion (CTP) techniques such as cerebral blood volume (CBV), time to peak (TTP), mean transit time (MTT) and cerebral blood flow (CBF) provide real time data about ischemia. It has been shown that CTP changes occur in less sensitive CTP scanners in patients with TIA. Larger detector row CTP (whole brain perfusion studies) may show that CTP abnormalities are more prevalent than previously noted. It is also unclear if these changes are associated with TIA severity.

OBJECTIVE

To demonstrate that TIA patients are associated with perfusion deficits using whole brain 320-detector-row CT perfusion, and to determine an association between ABCD2 score and perfusion deficit using whole brain perfusion.

METHODS

We retrospectively reviewed all TIA patients for CTP deficits from 2008-2010. Perfusion imaging was reviewed at admission; and it was determined if a perfusion deficit was present along with vascular territory involved.

RESULTS

Of 364 TIA patients, 62 patients had CTP deficits. The largest group of patients had MCA territory involved with 48 of 62 patients (77.42%). The most common perfusion abnormality was increased TTP with 46 patients (74.19%). The ABCD2 score was reviewed in association with perfusion deficit. Increased age >60, severe hypertension (>180/100 mmHg), patients with speech abnormalities, and duration of symptoms >10 min were associated with a perfusion deficit but history of diabetes or minimal/moderate hypertension (140/90-179/99 mmHg) was not. There was no association between motor deficit and perfusion abnormality.

CONCLUSION

Perfusion deficits are found in TIA patients using whole brain CTP and associated with components of the ABCD2 score.